This invention relates to boat hoists, generally, and, more specifically, to a hydraulic lift device for a boat hoist, in which the structure to which the principal components thereof are attached also provides a protective enclosure for those components.
A variety of prior art applications are known related to the function of vertically moving a suspended boat cradle by various means including some hydraulic applications. Such hoists are used in residential, recreational and light commercial settings, to lift a boat out of the water when not in use. In northern locales, these hoists must also be seasonably removable to prevent ice damage of hoist components at or below the water surface.
Prior art applications in the field have included variations of cantilever-style hoists. Many of these employ hydraulic cylinders below the water surface. Some hoists of this type have utilized large winches forward of the hoist to pull the hoist""s bed or cradle over its pivot point. There has been limited success, as well, with vertical lifts which utilize hydraulics or large cable winches.
Existing vertical winch lifts, typically may be outfitted with two or more winches, particulary for heavier weight applications, and these multiple winches may run at varying speeds, which may be disadvantageous.
Hydraulic vertical lifts of the existing art often use one cable to lift one corner of the lifting bed or cradle, using multiple leveling cable to equalize lift on all other corners. Existing hydraulic applications, as well, utilize the xe2x80x9cpullxe2x80x9d of the hydraulic cylinder, rather than the xe2x80x9cpushxe2x80x9d. Because of these factors most existing hydraulic lifting devices have significant load limitations.
Hydraulic cantilever lifts require substantial structure support because of compounded force at bottom of the lifting cycle. Significantly more power is required in the initial portion of the cycle than in the latter. It is also typical of the prior art that the hydraulics are beneath the water surface when the hoist is operated. This creates a number of disadvantages.
Below surface hydraulics are not only difficult to service, but are exposed to harsh elements, including sand, salt (in salt water applications), zebra muscles and barnacles. Below lift mechanical components will also require deeper water, which is a luxury not always available, because the lift bed may not be able to be placed as proximate to the bottom as is optimally desired. Because of their method of operation, and upper configuration, hydraulic cantilever hoists may also be difficult to accessorize with such important additions as canopies and motor and bow stops.
Winch cantilever hoists address some concerns, but present their own problems. Structure size and weight, to address strength requirements, limit mobility of the entire hoist assembly. They are also generally powered by 220 volt electricity which is potentially hazardous in a marine environment.
Representative of the prior art are U.S. Pat. No. 5,934,826 to Mansfield disclosing a combination boat lift apparatus and piling; U.S. Pat. No. 5,522, 671, to Keesling, disclosing a pair of hydraulic cylinders vertically mounted in conjunction with reinforced concrete pilings; U.S. Pat. No. 5,090,841, to Pench, Jr. et al, disclosing a hydraulic pump and cylinder on a manual boat lift; U.S. Pat. No. 4,773,346 to Blanding et al., disclosing vertically mounted hydraulic cylinders, at each corner of a boat hoist; and U.S. Pat. No. 4,641,596 to Reprogle et al., which discloses a combination of vertical hydraulic cylinders and moveable pulley blocks;
Accordingly, a need exists for a boat hoist hydraulic lift device which may be used in conjunction with an easily portable boat hoist to maximize mobility; which allows the lift bed of the hoist to rest as proximate to the bottom of the body of water as possible; which utilizes the xe2x80x9cpushxe2x80x9d as opposed to the xe2x80x9cpullxe2x80x9d of the hydraulic cylinder unit; which does not require 220 volt electrical power from an external source; which provides equal vertical xe2x80x9cliftxe2x80x9d directly to both ends of the lift bed; and which is constructed so that the primary mechanical and power components are located above the surface of the water and are otherwise shielded from the elements.
The present invention is so directed.
The present invention has been designed to the overcome the shortcomings in the prior art as noted above. It is directed to the provision of a significantly improved lifting device for utilization with in-water boat hoists.
More specifically, this invention is directed to a boat hoist hydraulic lift device which may be used in conjunction with currently existing boat hoist frames to provide a portable boat hoist which maximizes mobility.
An additional object of the invention is to provide a boat hoist hydraulic lift device which allows the lift bed of the hoist to rest as approximate as possible to the bottom of the body of water and, further is constructed so that the primary mechanical components are located above the surface of the water, and are shielded from other elements as well.
An additional object of the invention is to provide a hydraulic lift device which maximizes lifting power by utilizing the xe2x80x9cpushxe2x80x9d of a hydraulic cylinder, as opposed to the xe2x80x9cpullxe2x80x9d thereof. Further, the device is directed to provision of a hydraulic lifting function in an in-water boat hoist application which does not require 220 volt electrical power from an external source and which provides equal vertical lift directly to both ends of the lift bed.
The boat hoist lift device which is a primary object of the invention is utilized in conjunction with in-water boat hoists having a base frame, which is normally adjustable, to rest substantially horizontally on the bottom of a body of water. Such hoists are normally substantially rectangular in shape, with a lower rectangular base, and supporting shoes or skids, which have an adjustment means to level the lower portion of the hoist. The hoist itself has a plurality of stanchions which extend vertically, normally at the corners thereof, and along the sides. Stanchions are not normally provided along the ends of the hoist, as that is where the boat, or other load to be lifted, normally enters and exits.
In conjunction with the type of hoist described, the present invention, in an important feature, may utilize either one hydraulic lift device or a pair of such devices mounted in parallel, on opposite sides of the boat hoist.
According to a further important feature of the invention, each individual hydraulic lift device unit initially includes a support and enclosure unit, extending between upright stanchions of the boat hoist assembly itself, on one side of the boat hoist. This rigid unit provides the dual function of supporting the hydraulic lift device and its primary components, and further, enclosing those components and shielding them from the elements. This rigid support member is essentially a rigid, longitudinal box member, extending between upright boat hoist stanchions and includes joined and enclosed bottom, back, top, and end units. A front cover unit, which is removable, is also provided, for access to the components for service and maintenance.
According to a further feature of the invention, within the support structure enclosure, a hydraulic cylinder, which includes a cylinder body and extendable piston, is secured, in horizontal relationship. The cylinder body itself is located more closely to one end of the enclosure, and the piston rod is extended by hydraulic pressure, outwardly, toward the other end of the enclosure.
A further feature of the invention includes a vertical yoke member which is centered on and attached, by clevis, or other means, to the end of the piston rod. Two separate lift cables extend rearwardly, substantially in parallel, from the yoke at the end of the piston rod, towards the end of the enclosure where the cylinder body is located. One of the lift cables continues such horizontal extension to a point closely approximate to the end of the support enclosure member, where it is directed downwardly, at approximately a 90xc2x0 angle, over a fixed pulley. The other lift cable extends in the same initial direction, until it reaches a pulley affixed within the enclosure at, or beyond the point where the piston rod enters and exits the cylinder body. The cable is reversed on the pulley, and extends, in substantially a 180xc2x0 reversal, to another pulley located approximate to the opposing end of the support enclosure member. At that point it is directed downward approximately 90xc2x0 over another fixed pulley. Both cables extend through openings provided in the base of the support enclosure member substantially vertically downward and are connected, respectively, at opposite ends, thereof, to the lift bed.
It is a further feature of the invention that the extension of the piston rod from the hydraulic cylinder, for a specified distance, occasions a rise in the lift bed of the boat hoist of an equivalent distance.
Another important feature of the invention limits rotational movement of the yoke at the end of the piston rod, and limits upward or downward movement, as well, thus minimizing wear on the hydraulic cylinder, at the point where the rod enters and exits. It is a feature of the invention, that this is accomplished by utilization of two tracks, which may be extruded ridges, a separate xe2x80x9cC-channelxe2x80x9d member in parallel with the piston rod, or other upper and lower track means, which contact the yoke at the end of the piston rod in a manner which allows it to slide back and forth horizontally, but which do not allow rotational, or vertical movement.
It is another feature of the invention, that, when a single hydraulic lift device is utilized on one side of a boat hoist assembly, with lift cables affixed to each end of the lift bed, of the hoist assembly, that the lift bed may be maintained in a substantially horizontal position, by utilization of one or more leveling cables. Each leveling cable is affixed to the upper end of a vertical stanchion, on the side of the boat lift opposite the location of the support enclosure member and primary components. The leveling cable runs substantially vertically down to the lift bed, where it contacts a pulley and is guided, directionally, approximately horizontally, along one end of the lift bed to the opposite side thereof, where it contacts another pulley and is thereby directed approximately 90xc2x0 downwardly, where the cable is affixed to the base of the boat hoist either on the end of vertical stanchion or approximate thereto. The leveling cables may be used on either or both ends of the hoist assembly, and are optimally used on both. When one hydraulic lift device is utilized, with leveling cables at both ends, each leveling cable commences by attachment at the top of the end stanchion on the opposite side of the lift from the device, and runs, as stated, to the lower corner of the hoist assembly on the side where the hydraulic device is located.
According to a further feature of the invention, when a pair of hydraulic lift devices are utilized in parallel on opposite sides of the boat hoist assembly, the leveling cable at one end of the boat lift will commence affixed to the top of an end stanchion on one side of the boat lift, and the other end leveling cable will commence at the top of a stanchion on the opposing side of the hoist.
The leveling cables are installed and maintained under static tension.
It is a further feature of the invention that a power source for operating one or both hydraulic cylinders is self contained within the enclosure member and the hydraulic cylinder, either singly, or in parallel when two are provided, and may be activated by means of a self-contained on/off switch and, in some applications such on/off switch or function may be accomplished by utilization of radio frequency receiver unit located adjacent one of the cylinder bodies, within the enclosure member and a remote radio frequency sender unit.
A further feature of the invention, is that the self-contained power source may be a 12 volt battery affixed within the support enclosure member and, as a further feature of the invention the power source may be replenished by means of a rigid solar panel connected thereto, and outwardly affixed on the exterior of the hoist assembly. It is a further feature of the invention that where a pair of hydraulic lift devices are utilized in parallel, a single power source and common means of activating the hydraulic cylinders may be utilized.